Corrosion Control Treatment
Lead and copper enter drinking water primarily through corrosion of home and building plumbing materials. In the Portland area, lead-containing plumbing materials are most commonly found in buildings built or plumbed between 1970 and 1985 with copper pipes and lead solder. Fixtures, such as faucets, installed prior to 1985 can also contribute to elevated lead in water. Faucets and fixtures installed before 2014 can also contain up to 8% lead.
Untreated water from the Bull Run Watershed is naturally corrosive, which can increase the amount of lead and copper that dissolves from home plumbing into drinking water. Since 1997, the Portland Water Bureau’s corrosion control treatment has reduced corrosion in plumbing by adding sodium hydroxide, which increases the pH of the water to 8.1. This treatment has been shown to reduce the presence of lead in tap water up to 70%. This treatment is applied to water from both of Portland’s water sources, the Bull Run Watershed and the Columbia South Shore Wellfield.
In 2014, in anticipation of changes to the water system, the Portland Water Bureau embarked on a water quality corrosion study. This study will inform potential changes in the future. We expect results from the study in early 2017. Preliminary results indicate that treatment improvements can be effective at reducing the levels of lead in water. As a result, the Portland Water Bureau is working with state and federal health officials to develop a schedule for implementing additional corrosion control. These changes are anticipated to be implemented in the next 3 to 4 years.
Twice each year the Portland Water Bureau and regional water providers in the Bull Run service area test more than 100 high-risk homes to monitor the effectiveness of corrosion control for lead and copper in tap water. These high-risk homes are known to contain copper pipes and lead solder, which is more likely to contribute to elevated lead levels. These homes represent a worst-case scenario for lead in water.
Sample collection instructions for the homeowners follow Environmental Protection Agency (EPA) recommended procedures. Samples are collected by the homeowners after the water has been standing in the household plumbing for more than 6 hours. When samples are returned to the Water Bureau, they are put through a screening process to ensure they meet the regulatory requirements before being sent to the lab. This ensures that the results from all the samples analyzed by the lab will be used to determine compliance with the Lead and Copper Rule and will not be invalidated due to sampling issues. If lead levels are over 15 parts per billion*, the action level established by the Environmental Protection Agency to monitor the effectiveness of corrosion treatment, in more than 10% of these homes, the Portland Water Bureau notifies its customers and performs outreach and education to those most at-risk for lead exposure. In the most recent round of monitoring, more than 10% of homes were above the action level for lead in water.
*One part per billion corresponds to one penny in $10,000,000 or approximately one minute in 2,000 years.
High-Risk Home Monitoring Results